Power supply apparatus for an electrical appliance

ABSTRACT

A power supply apparatus includes a power supply circuit and a power-on circuit. The power-on circuit detects a remotely transmitted control signal and causes a transition of the power supply circuit to a turned on state. The power-on circuit includes a transducer configured to provide a power-on signal in response to the remote control signal. The transducer triggers transition to the turned on state through a switch driven by the power-on signal output from the transducer and arranged to supply a power supply circuit enable signal. A DC blocking capacitor is connected between an output of the transducer and a control terminal of the switch.

PRIORITY CLAIM

This application claims priority from Italian Application for Patent No.MI2012A001436 filed Aug. 21, 2012, the disclosure of which isincorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a power supply apparatus for anelectrical appliance.

BACKGROUND

As is known, many electrical or electronic appliances envisage aslow-consumption mode of operation, referred to as “stand-by mode”. Inthis mode, the electrical appliance is inactive as regards its normaloperation (for example, display of images for a television set, soundreproduction for hi-fi equipment, etc.) but can be controlled inswitching-on through a remote control. As is generally known, anelectrical appliance in stand-by mode is in any case supplied throughthe electric-supply mains, such as domestic power. The energyconsumption is due to the presence of a microcontroller, configured toreceive and process possible commands issued by a remote controller andsupplied for this purpose.

Considerable efforts have been made in the last years to limit currentconsumption in stand-by mode of electrical appliances, which, so far,generally have levels of consumption of a few watts. However, it isevident that, if the consumption in stand-by mode of a plurality ofelectrical appliances generally present in dwellings is considered,non-negligible daily consumption levels may be reached.

It is known from PCT Application No. WO2010/106113 (the disclosure ofwhich is incorporated by reference), and shown in FIG. 1 herein, a powersupply circuit for an electrical appliances. The power supply circuit 30in FIG. 1, in particular a switch-mode power supply (SMPS) circuit of aflyback type, comprises a remotely activated start-up circuit 32connected to a capacitor 18, which is in turn connected to a groundreference voltage GND. The start-up circuit 32 comprises a turn-ontransistor 15 and a transducer 33, which can be remote-controlled and isconfigured to power-on, when activated, passage of a current therethough. The transducer 33 is connected between a drain terminal D and agate terminal G of the turn-on MOS transistor 15. The transducer 33 canbe a photodiode configured so as to power-on passage of a currentthrough it if activated by a light beam at a particular wavelength orwithin a range of wavelengths. The turn-on circuit 32 also comprises aturn-off resistor 34 connected between the gate terminal G and thesource terminal S of the turn-on transistor 15; finally a Zener diode 35is connected between the gate terminal G and the source terminal S ofthe turn-on transistor 15, in parallel to the turn-off resistor 34.

SUMMARY

One aspect of the present disclosure is to provide a power supplyapparatus wherein the circuit performances are improved with respect tothe prior art. Particularly the power supply apparatus provides improvedcircuit performances of the power-on circuit of the power supplyapparatus itself.

One aspect of the present disclosure is a power supply apparatus for anelectrical appliance comprising a power supply circuit and a power-oncircuit of the power supply circuit, said power-on circuit beingconfigured for determining a transition from a turned off state, whereinsaid power supply circuit is off and does not supply electric power, toa turned on state of said power supply circuit, said power-on circuitcomprising a transducer of a remote-controlled type configured toprovide an power-on signal to trigger said transition in response to areception of a wireless signal, said power-on circuit comprising aswitch arranged in the electric path between an external DC supply lineand the output terminal of the power-on circuit, said switch beingdriven by the transducer, wherein said power-on circuit comprises acapacitor arranged between the output terminal of the transducer and thedriving terminal of the switch and configured so that the switch is notDC coupled with the transducer.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, preferredembodiments thereof are now described, purely by way of non-limitingexample and with reference to the annexed drawings, wherein:

FIG. 1 shows a switch-mode power supply circuit of a known type formanaging remote turning-on of an electrical appliance;

FIG. 2 shows a functional block diagram of an electrical appliance thatimplements a power supply apparatus;

FIG. 3 shows a power supply apparatus for an electrical applianceaccording to a first embodiment of present disclosure;

FIG. 4 shows only the power-on circuit of the power supply apparatus foran electrical appliance according to a second embodiment of presentdisclosure; and

FIG. 5 shows only the power-on circuit of the power supply apparatus foran electrical appliance according to a third embodiment of presentdisclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 2 shows a functional block diagram of an electrical appliance 50and a remote control 57. The electrical appliance 50 may, for example,be an audio/video system such as a television set, a hi-fi system, avideo recorder, or an electrical household appliance in general, whichimplements a power supply apparatus 300. In particular, the remotecontrol 57 is configured for issuing an appropriate power wirelesssignal for the remote activation of a transducer of the power supplyapparatus 301, in order to turn-on the electrical appliance 50.

The electrical appliance 50 of FIG. 2 is supplied by means of the powersupply apparatus 301 comprising a main power supply circuit 300, forexample a switch-mode power supply (SMPS) circuit of a flyback type,coupled with the electric-supply line Val by means of a rectifier 9, forexample a diode rectifier bridge with a filter capacitor. The rectifier9 is connected to the supply line Val and outputs a DC working voltageV₁ which is at the input supply terminal 12′ of the main power supplycircuit 300.

The power supply apparatus comprises a power-on circuit 100 of the powersupply circuit 300. The power-on circuit 100 is arranged between the DCworking voltage V₁ and the power-on terminal 18′ of the power supplycircuit 300.

The power-on circuit 100 is preferably external to the supply circuit300, but may be integrated with the same supply circuit 30, and isconfigured to provide a power on signal through an output terminalOUT_EN to the supply circuit 300 through said power on terminal 18′,separated from said input supply terminal 12′.

The electrical appliance 50 then comprises: a microcontroller 5, whichis connected to the power supply circuit 300 from which it receives thesupply, and communicates with a command sensor 6; a sound-reproducingcircuit 51, which is connected to the power supply circuit 300 fromwhich it receives the supply, and communicates with the microcontroller5 and with one or more loudspeakers 55; optionally a memory 52, which isconnected to the power supply circuit 30 from which it receives thesupply, and communicates with the microcontroller 5, for storingpossible programming information of the electronic appliance 50; and,optionally, a video-reproducing circuit 53, which is connected to thepower supply circuit 300 from which it receives the supply, andcommunicates with the microcontroller 5 and is configured for managingdisplay of graphic information or images on a display 54.

The power-on circuit 100 processes the power on signal emitted by theremote control 57 so as to determine a transition from a turned offstate, wherein said power supply circuit 300 is off and does not supplyelectric power, to a turned on state of said power supply circuit. Thepower-on circuit comprises a transducer 37 of a remote-controlled typeconfigured to provide a power-on signal OUT_EN to trigger saidtransition in response to a reception of a wireless power signalderiving from the remote control 57.

FIG. 3 shows in more detail the power supply apparatus 301 for anelectrical appliance according to a first embodiment of presentdisclosure. The DC working voltage V₁ is supplied in input to the powersupply circuit 300, particularly to a primary winding 12 of atransformer 11. The primary winding 12 comprises the terminal 12′connected to the rectifier 9 and another second terminal 12″. The secondterminal 12″ is connected in series to a not drivable terminal D1 of aswitch 15, for example the drain of a MOS device, the other not drivableterminal S1 (for example, the source) of which is connected to groundGND.

The switch 15 is controlled in conduction and interdiction by a drivingcircuit 19 the output terminal of which is connected with the drivableterminal G1, that is the gate terminal of the MOS transistor 15. Thedriving circuit 19 is moreover connected, through an input terminalthereof, to the input power-on terminal 18′; therefore the power-oncircuit 100 directly controls the driving circuit 19 of the switchingtransistor of the supply circuit 300. A turn-on capacitor 18 is alsoconnected between said power-on terminal 18′ and ground GND; from saidcapacitor 18 the driving circuit 19 receives the supply during itstuning-on step. The input terminal of the driving circuit 19 is moreoverconnected, via a rectifier diode 22, to an auxiliary winding 21 of thetransformer 11, which supplies the driving circuit 19 during use, afterthe turning-on step.

The power-on circuit 100 comprises transducer 37, preferably a lightsensor, which drives a switch 38; the switch 38 is connected between theDC supply line V₁ and the output terminal OUT_EN, which is normallyconnected with the input terminal 18′ of power supply circuit 300,particularly with the common terminal of the capacitor 18 and the inputterminal of the driving circuit 19.

The light sensor 37 can be made either by a reverse biased photodiode,or a plurality of photodiodes connected in series one another, or aphototransistor configured so as to power-on passage of current acrossits terminals if activated by a light beam at a particular wavelength.For simplicity of description, in what follows reference will be made toa photodiode, more precisely which can be activated by an infrared beam.

The photodiode is modeled with a current generator 39, which takesaccount of the current generated by the infrared beam, in parallel witha diode 40 which describes internal recombination. The switch 38 is madewith an high voltage transistor 41, for example of a MOSFET type, and aZener diode 42, connected between the gate terminal G of the transistor41 and the output terminal OUT_EN, being said Zener diode 42 able tolimit the potential applied to the gate terminal G of the transistor 41to a maximum value represented by the voltage V_(ZENER), proper to theZener diode 42.

A resistor 45 is connected between the gate terminal G of the transistor41 and the ground GND, said resistor 45 being suitable to convert thecurrent generated by the photodiode 37 into a voltage.

Finally the transformer 11 comprises a secondary winding 24 forgenerating on an output port of the power supply circuit 4 an outputvoltage V_(OUT) that supplies the microcontroller 5 and others.

In use, with reference to FIG. 3, when the phototransistor 37 is drivenin conduction by means of an incident light beam having a wavelength inthe infrared, a current flows through it and a voltage develops acrossits terminal, biasing the gate terminal G of the transistor 41. If thebiasing voltage generated by the resistors 45 is higher than theconduction threshold of the turn-on transistor 41, the transistor 41turns on and the switch 38 closes; the DC working voltage V₁ is now sentthrough the terminal OUT_EN to the input power-on terminal 18′ of thesupply circuit. In this way, the turn-on capacitor 18 is charged (FIG.3) and, when the voltage on the turn-on capacitor 18 reaches a valueV_(C) sufficient to supply the driving circuit 19, the driving circuit19 turns on and drives in conduction the switching transistor 15. Hence,the driving circuit 19 is supplied by the auxiliary winding 21.

After the turning-on step, the driving circuit 19 controls in conductionthe switching transistor 15. In this way, a current flows through theprimary winding 12 of the transformer 11 and supplies, via the auxiliarywinding 21, the driving circuit 19 itself. In use, the switchingtransistor 15 can be controlled via square-wave modulation (pulse-widthmodulation—PWM) signal with variable frequency and power-on transferonto the secondary winding 24 of the supply for operation of themicrocontroller 5. The sound-reproducing circuit 51, the memory 52, thevideo-reproducing circuit 53, the display 54, and the loudspeakers 55can be supplied by means of respective secondary windings (notillustrated) of the transformer 11 of the power supply circuit 30 ofFIG. 2.

The power-on circuit 100 comprises a capacitor 43 coupled between thetransducer 37 and the switch 38, particularly to the output terminal 40″of the transducer 37 and the drivable terminal G of the switch 38,particularly the gate terminal G of the MOS transistor 41 of the switch38; said capacitor 43 is configured so that the transducer 37 is not DCcoupled with the switch 38, that is said capacitor 43 has a value suchas to ensure that the switch 38, particularly the transistor 41, is notDC coupled with the transducer 37, in this way limiting the circuitrystart-up due to the static environmental light.

FIG. 4 shows only the power-on circuit 101 of the power supply apparatusfor an electrical appliance according to a second embodiment of presentdisclosure; differently from the power-on circuit 101 in FIG. 3, thepower-on circuit 101 comprises a resistor 44 connected to the DC supplyvoltage V₁ and the drain terminal D of the transistor 41; the resistor44 provides to rise up the output voltage at the terminal OUT_EN atsmall controlled steps, this for limiting the current into the capacitor18 configured to develop a supply voltage V_(C) adapted to turn on thepower supply circuit 30. A definable number of voltage steps are soneeded before the voltage at the input power-on terminal 18′ issufficient to start up the driving circuit 19. In this case, only awell-defined sequence of light events would start up the power supplycircuit 30 and not any undesired dynamic light event. Thus, just addinga well-defined resistor 44 would give more immunity to the circuitagainst undesired light events.

FIG. 5 shows only the power-on circuit 102 of the power supply apparatusfor an electrical appliance according to a second embodiment of presentdisclosure; differently from the power-on circuit 101 in FIG. 4, thepower-on circuit 102 solves the problem that in some environments, wherethe power light is so high, the voltage at the node 40″ could reach thevoltage value V₁, thus saturating the receiver. In this case the systemcannot respond to any further injection of light through the remote 57.The power-on circuit 102 comprises a negative feedback network 200 (FIG.5) connected between the output terminal 40″ of the transducer andground GND; the negative feedback network 200 is implemented by addingin series to the resistor 45 a resistor 46 and connecting a transistor47, for example a MOSFET, so that the gate terminal G2 of the MOStransistor 47 is connected with the common terminal of the resistances45, 46, the source terminal S2 of the transistor 47 is connected toground GND and the drain terminal D2 is connected to the terminal 40″ ofthe transducer 37. Transistor 47 will turn on when the photo current isso high that the voltage value at its gate terminal G2 is higher thanits voltage threshold. Thus transistor 47 will turn on only when theenvironment light is higher than a certain value that can be definedcase by case. Once the transistor 47 is on, a negative feedback willkeep down a node 40″ and fixed to a given value. In fact, if the photocurrent increases also the voltage across the resistor 46 increases andthe node 40″ is pulled down by the transistor 47. The resistor 44, evenif shown in FIG. 5, can belong or cannot belong to the power-on circuit102.

With the proposed power-on circuit is possible to solve several problemsin order to achieve a solid and reliable system able to work under themost diverse light environmental conditions, reducing to zero watt thepower consumption of an electronic appliance when in stand-by mode.

What is claimed is:
 1. A power supply apparatus for an electricalappliance, comprising: a power supply circuit; a power-on circuit of thepower supply circuit, said power-on circuit configured to determine atransition from a turned off state, wherein said power supply circuit isoff and does not supply electric power, to a turned on state of saidpower supply circuit; said power-on circuit comprising a transducer of aremote-controlled type configured to provide a power-on signal totrigger said transition in response to a reception of a wireless signal;said power-on circuit further comprising a switch arranged in anelectric path between an external DC supply line and an output terminalof the power-on circuit, said switch being driven by the transducer, andfurther comprising a capacitor arranged between an output terminal ofthe transducer and a control terminal of the switch and configured sothat the switch is not DC coupled with the transducer.
 2. The apparatusaccording to claim 1, wherein said power supply circuit comprises aninput power-on terminal and said power-on circuit is external to thepower supply circuit and is configured to provide said power-on signalto said input power-on terminal of the power supply circuit through theoutput terminal of said power-on circuit, said power supply circuitcomprising an input supply terminal separated from said power-onterminal and which is connected to an external DC supply line.
 3. Theapparatus according to claim 1, wherein said transducer comprises areverse biased photodiode activated by an infrared beam, said photodiodebeing modeled with a current generator which takes account of thecurrent generated by the infrared beam and a diode which describesinternal recombination.
 4. The apparatus according to claim 1, whereinsaid switch comprises a high voltage transistor and a Zener diode,arranged between a control terminal and a first not drivable terminal ofsaid high voltage transistor of the switch, said Zener diode configuredto limit the potential applied to the control terminal of saidtransistor.
 5. The apparatus according to claim 1, wherein said power-oncircuit comprises a resistor coupled to the control terminal of saidswitch and to a reference voltage to convert the current generated bythe transducer into a voltage.
 6. The apparatus according to claim 1,wherein said power-on circuit comprises a resistor arranged so as toconnect said switch with said external DC supply line, said resistorconfigured to limit the current delivered through the output terminal ofthe power-on circuit.
 7. The apparatus according to claim 1, whereinsaid power-on circuit comprises a negative feedback network coupled tothe output terminal of the transducer.
 8. The apparatus according toclaim 7, wherein said negative feedback network comprises a series oftwo resistors and a transistor having a control terminal connected tothe common terminal of the resistors of the series, a first not drivableterminal coupled to the output terminal of the transducer and a secondnot drivable terminal connected to a voltage reference, said series oftwo resistors being coupled between the output terminal of thetransducer and said voltage reference.
 9. The apparatus according toclaim 1, further comprising a remote control configured to generate saidwireless signal.
 10. A power supply apparatus, comprising: a powersupply circuit; a power-on circuit configured to control transitioningof the power supply circuit from a turned off state to a turned onstate; said power-on circuit comprising: a transducer of aremote-controlled type configured to provide an enable signal triggeringtransitioning of said power supply circuit in response to a detection ofa wireless control signal; a transistor switch having a control terminalcoupled to receive the enable signal and having a conduction terminalconfigured to generate a signal control transitioning of the powersupply circuit; a capacitor coupled between an output of the transducerand the control terminal of the transistor switch.
 11. The apparatusaccording to claim 10, wherein said transducer comprises an infraredphotodiode.
 12. The apparatus according to claim 10, further comprisinga zener diode coupled the control terminal and the conduction terminal.13. The apparatus according to claim 10, further comprising a resistorcoupled between the control terminal of the transistor switch and to areference voltage node.
 14. The apparatus according to claim 10, furthercomprising a resistor coupled between voltage supply node and anadditional conduction terminal of said transistor switch.
 15. Theapparatus according to claim 10, further comprising a negative feedbacknetwork coupled to an output terminal of the transducer.
 16. Theapparatus according to claim 15, wherein said negative feedback networkcomprises: a voltage divider circuit; a transistor having a controlterminal coupled to a tap node of the voltage divider circuit, a firstconduction terminal coupled to the output terminal of the transducer anda second conduction terminal coupled to voltage reference node.